Oxidative conversion including dehydrogenation

ABSTRACT

Oxidative conversion of olefins and/or diolefins including the dehydrogenation of organic compounds is carried out with an ironphosphorus-oxygen catalyst wherein the amount of phosphorus is greater than the stoichiometric amount required to react with all of the iron in the catalyst and form monophosphate ions (PO4 3). The activity of the phosphorus-containing catalyst can be maintained by continuous or intermittent addition of phosphorus containing compounds.

Umted States Patent 1 1 1111 3,716,545

Ripley 51 Feb. 13, 197 3 541 ()XIDATIVE NVE 3,207,809 9/1965 Bajars ..260/680 INCLUDING DEHYDROGENATION 3,210,436 10/1965 Bajars et a1. ..260/680 3,308,193 3/1967 Bajars ..260/680 lnvemori Dennis p y Bartlesville, Okla- 3,555,105 1 1971 Nolan et a1 ..260/680 A ig Petroleum p y 1,882,712 Andrussow et a1. [22] Filed: Jan. 16, 1970 App]. No.: 4,470

Related US. Application Data Continuation of Ser. No. 769,428, Oct. 21, 1968, abandoned, which is a continuation-in-part of Ser. No. 693,186, Dec. 26, 1967, abandoned.

[56] References Cited UNITED STATES PATENTS 3,110,746 11/1963 Voge et al. ..260/680 Primary Examinerlaul M. Coughlan, Jr. AttorneyYoung and Quigg [5 7] ABSTRACT Oxidative conversion of olefins and/or diolefins including the dehydrogenation of organic compounds is carried out with an iron-phosphorus-oxygen catalyst wherein the amount of phosphorus is greater than the stoichiometric amount required to react with all of the iron in the catalyst and form monophosphate ions (PO The activity of the phosphorus-containing catalyst can be maintained by continuous or intermittent addition of phosphorus containing compounds.

16 Claims, No Drawings OXIDATIVE CONVERSION INCLUDING DEHYDROGENATION This application is a continuation of copending application Ser. No. 769,428 filed Oct. 21, 1968, now abandoned, which was a continuation-in-part of copending application, Ser. No. 693,186, filed Dec. 26, 1967, now abandoned.

This invention relates to oxidative conversion including dehydrogenation. In another aspect, this invention relates to a new and improved oxidative conversion catalyst and oxidative conversion process. ln still another aspect, this invention relates to maintaining the activity of an oxidative conversion catalyst. The term oxidative conversion" as used in this application includes oxidative dehydrogenation.

Oxidative conversion processes are usually operated at the highest possible conversion consistent with a high selectivity to desired product. Such operation minimizes the required separation facilities, which is highly desirable from both an economic and operating viewpoint. The percentage conversion is defined as 100 times the moles of feedstock destroyed or otherwise converted divided by the moles of feedstock entering the process, and the percentage selectivity is defined as one hundred times the moles of desired product produced divided by the moles of feedstock destroyed or otherwise converted.

One means of evaluating the efficiency of an oxidative conversion catalyst is to add the percentage conversion and selectivity to obtain a conversion selectivity value. Under constant operating conditions, comparison of the conversion-selectivity (CSV) values for a number of catalysts enables one to select those catalysts capable of giving the best overall performance in actual operation.

One of the major shortcomings of conventional ironphosphate oxidative conversion catalysts is that the percentage conversion and percentage selectivity are both generally quite low. This requires the working up of large amounts of material to recover oxidative converted products, and generally a sizable recycle which further increases the size of the oxidative conversion equipment.

One object of this invention is to provide an improved oxidative conversion process.

Another object of this invention is to provide an improved iron-phosphorus-oxygen oxidative conversion catalyst, the use of which results in increased conversion-selectivity values.

Still another object of this invention is to maintain the activity of the oxidative conversion catalyst.

According to this invention, 1 have discovered that if iron-phosphorus-oxygen catalyst systems are prepared to have phosphorus contents in excess of the stoichiometric amount required for the phosphate to react in the form of phosphate ions (POfi) with all the iron in the catalyst, improved highly active catalysts are formed. Thus, depending on the valence of the iron, my improved catalyst has a phosphorus content higher than that calculated for the corresponding iron compound containing phosphate ions. Although the invention is not to be limited thereby, it is my theory that at least part of the phosphorus is present as phosphate anions or mixtures of such anions having the empirical formulas in which n is an integer in the raNge of 2 through 100. The iron within the catalyst compositions of this invention can be in the ferric, ferrous, or ferroso-ferric forms and will have phosphorus contents higher than that calculated for the compound containing only phosphate ions:

Considered to be derived from magnetic iron oxide (Fe-,0, or FeO'Fe,BS3).

Thus, the catalysts of this invention are ironphosphorus-oxygen compositions in which the phosphorus content is generally in the range of from 1.001 to 5, preferably 1.01 to 2 times the stoichiometric amount required to react with all of said iron in the form of phosphate (PO, ions, and the oxygen to phosphorus atomic ratio therein is in the range of from 3/1 to 3.999/1.

The catalysts of this invention can be prepared in a number of ways, preferably by the treatment of iron oxides, hydroxides, phosphates, or other salts with phosphoric acid, or by dry mixing of iron oxides or iron salts with P 0 and the like. If desired, other methods can be used such as, for example, precipitation of iron phosphates such that the finished catalysts contain excess phosphorus. An example of this process would comprise forming a polyphosphate anion by heating alkali or ammonium dihydrogen phosphate to a temperature in the range of from about 200 to l,000 C and then adding ferric or ferrous iron to the resulting solution.

The catalysts of this invention can be used in any conventional oxidative conversion process. Illustrative oxidative conversion processes are those that convert 'olefins into diolefins and oxygenated compounds such as furans, furfural, acetaldehyde, pyrans, acetic acid, acrylic acid, methyacrylic acid, acrolein, methacrolein, c'rotonaldehyde, crotonic acid, acetone, ethanol, and the like, and those which convert diolefins into the listed oxygenated compounds. Suitable oxidative conversion processes are those that convert at least one material selected from the group consisting of alkenes, alkadienes, cycloalkenes, cycloalkadienes, alkylpyridines, and alkylaromatics to less-saturated and/or oxygen-containing products using an elevated temperature, and a molecular oxygen-containing gas, with or without the presence of steam. It is within the scope of the invention to convert oxygen-containing compounds to compounds having a greater oxygen content. For example, methacrolein can be converted to methacrylic acid. The alkenes and alkadienes can contain from three to 10, preferably four to six, carbon atoms per molecule, inclusive, and the cycloalkenes and cycloalkadienes can contain from four to 10, preferably four to six, carbon atoms per molecule, inclusive. The alkylpyridines and alkylaromatics can contain from one to four, preferably from one to two, alkyl groups per molecule which themselves contain from one to six, preferably from two to six, carbon atoms per group, inclusive, with at least one alkyl group having at least two carbon atoms. This process is operable with alkenes and alkadienes having three to carbon atoms, such as propylene, n-butenes, isobutylene, n-pentenes, isopentene, octenes, decenes, propadiene, 1,3-butadiene, isoprene, l,3-pentadiene, 1,5-hexadiene, 1.9- decadiene, and the like. Examples of cycloalkenes and cycloalkadienes that can be used are cyclobutene, cyclopentene, cyclohexene, 3-isopentylcyclopentene, cyclopentadiene, 1,4-cyclohexadiene, and the like. Examples of alkyaromatics that can be used are ethylbenzene, propylbenzene, n-butylbenzene, isobutylbenzene, hexylbenzene, l-methyl-2-propylbenzene, lbutyl-3-hexylbenzene, and the like. Examples of alkylpyridines that can be used are ethylpyridine, 2-methyl- S-ethylpyridine, 2,3,4-triethylmethyl-5-ethylpyridine, 2-ethy-5-hexylpyridine, and the like.

Preferred reactions applicable to this invention are the formation of 1,3-butadiene from butenes, 1,3-pentadiene from pentenes, isoprene from isopentenes, styrene from ethylbenzene, 2-methyl-5-vinylpyridine from 2-methyl-5-ethylpyridine, furan and acetaldehyde from butenes and/or 1,3-butadiene, and furfural, acetaldehyde, and acetic acid from pentenes and/or pentadienes. It is apparent that an olefin feed, a diolcfin feed, or a mixed olefin/diolefin feed resulting from at least partial recycle of the products of reaction, can be used. Although oletins and/or diolefins can be recycled to extinction, it is presently preferred to recover oxygenated products and diolefins and to recycle only the olefins.

The catalysts of this invention can be used in the form of granules, mechanically formed pellets, or any other conventional form for catalysts. The catalysts can also be employed with suitable supporting or diluting materials such as silica, alumina, boria, magnesia, titania zirconia, and combinations thereof, such as silica-alumina, boria-alumina, silica-magnesia, and the like, and similar conventional materials known in the art.

The amount of catalysts employed will vary widely depending upon the material present and the conditions but generally the amount will be that which, for the given reaction, is an effective catalytic amount to produce the desired oxidative conversion results.

The molecular oxygen-containing gas employed can be present as such or with inert diluents such as nitrogen and the like. Suitable molecular-oxygen containing gases include air, flue gases containing residual oxygen, and the like. If desired, pure or substantially pure oxygen can also be employed.

The operating conditions of the process of this invention can vary widely but will generally include a temperature in the range from about 700 to about 1,300" P, preferably from about 800 to about l,200 F; a pressure in the range of from about 0.05 to about 250, preferably from about 0.1 to about 25 psia; and oxygen-to-gaseous organic compound feed volume ratio in the range of from about 0.1/1 to about 3/], preferably from about 0.5/1 to about 2/1; and, if steam is used, a steam-to-organic feed volume ratio in the range of0.l/l to /1, preferably 5/! to 20/1. The organic compound feed space rate (volumes of organic compound vapor/volume of catalyst/hour, 32 F, 14.7 psia) can be from about 50 to about 5,000, preferably from about 100 to about 2,500.

The process of this invention is ordinarily carried out by forming a mixture, preferably preheated, of organic compound feed, steam, if used, and oxygen or oxygencontaining gases, and passing this mixture over the catalyst at the desired temperature. Recycle of unconverted organic compound feed and/or steam condensate can be employed if desired; however, the conversion rates and selectivity of this invention are generally sufficiently high to eliminate necessity for recycle.

The following examples are given to further illustrate this invention. As is illustrated by the examples, there is a gradation in oxidative conversion activity as phosphorus content of the catalyst system increases from that required for monophosphate formation with the iron to above that required for the monophosphate formation with the iron. in all of the examples, conversion and percentage selectivity values were determined by gas-phase chromatography and are given in mol percent; therefore, the selectivity is a gas-phase value, i.e., the small amount of material remaining in the steam condensate receiver following the reactor is neglected. The values given in Examples I-lV are for an on-stream time of 1 hour. Those in Examples VlII-Xl are for an on-stream time of 20 minutes.

The catalysts of the invention can be used for long periods without reactivation. However, if or when reactivation becomes necessary, it can be effected simply by stopping the flow of organic compound and allowing the flow of the other components of the feed mixture to continue for the desired reactivation period. However, a preferred method of reactivation can be accomplished by the continuous or intermittent addition of phosphorus-containing compounds to the catalysts. The process of this invention is illustrated by addition of phosphoric acid or phosphorus pentoxide, but other compounds of phosphorus such as other acids, anhydrides, phosphines, and organophosphorus compounds such those listed in 30 Chemical and Engineering News 4515ff (1952), can also be used. The phosphorus addition can be done alone, or in conjunction with intermittent catalyst regeneration with air or steam/air. The rate of addition of the phosphorus-containing compound is such that the phosphorus content of the catalyst is maintained at the same level as that of the catalyst as charged to the reactor or is adjusted to any desired content within the range recited herein. Inasmuch as any phosphorus lost from the catalyst appears in the steam condensate from the reactor, it is within the skill of the art to analyze that condensate and to calculate the amount of phosphorus compound required either to replace the phosphorus lost or to change the phosphorus content of the catalyst in the reactor. The phosphorus compound can be added as solid, liquid, or gas, or can be added as a solution or suspension in a suitable solvent or diluent such as water or an organic compound such as that being converted or any other organic compound not deleterious to the reaction being effected.

in the runs described in Examples llV, Z-methylbutene-2 was dehydrogenated to isoprene at feed, air, and

steam space rates of 200, 1,000, and 5,000, respectively, a temperature of l,000 F, and essentially atmospheric pressure. The catalysts used in all examples except Example Vll were in the form of 20-30 mesh phosphorus than that required for formation of ferrosoferric phosphate are considerably more active than the one having the theoretical phosphorus content.

EXAMPLE 111 Catalyst 9 was prepared in the following manner: 515.4 parts by weight of Fe(NO,) -9H,O was dissolved in 1,000 parts by weight of deionized water and s'eve) matenal' ac1d1f1ed w1th l57.5 parts by welght of aqueous n1tr1c acid (71 wt. percent HNO To this solution was added EXAMPLE 1 another solut1on of 115 parts by weight of NH H,PO A series of catalysts was prepared by adding various dissolved in l,000 parts by weight of deionized water. amounts of concentrated aqueous phosphoric acid (85 10 Aqueous ammonium hydroxide (about 28 weight perweight percent H P0 to aqueous slurries of ferric ox- Cent a) was then added Untll e P r ached 6- The ide, drying at 240 F in i and whining at 1 00 F in prec1p1tate was filtered and washed 3 t1mes w1th 1,000- air. Preparation details and oxidative conversion results Parts by i Pf of deionized water- T filter are: cake was d1v1ded into 4 equal port1ons, 3 of wh1ch were impregnated with aqueous phosphoric acid (85 wt. per- Time cent) while in the hydrous form. All portions were cal- Amount Used, pbw(c)hours cined 2 hours at 1,000 F. The amount of 85 percent c 85% d C a phosphoric acid added to each portion, the phosphorus at. ryc1nwt No. Fegoam HOHSPO ing in (a) Con Selec CSV content, and the oxidative convers1on results are.

catalyst l 30 40 47.6 40 22 20.5 62 71 I33 No. 85% H PO Added,pbw P,wt%(a) conv. selec CSV 2 20 54.4 20.7 73 82 I55 3 40 54.4 2l.7 93 74 I67 9 20 5 31 96 I27 4 40 6L2 22.5 75 84 159 5 40 580 no 78 86 64 l0(b) 17.0 24.7 61 95 156 ll 17.0 24.9 70 87 l57 12 59.5 28.5 79 85 I64 (a) Theoretical for FePO, 20.5 percent. (b) Fisher ferric oxide, item l-l l6, Catalog No. 64-C. This material (a)Theoreticalfor'FePO =20.5 weight percent. was used in preparing catalyst 1-5. (b) Dried at 240F for 5 hours before calcining. (c) Parts by weight.

l It is apparent once again that those catalysts containing It 15 pp that those catalysts comammg more more phosphorus than that required for formation of phosphorus than that required for formation of ferric ferric phosphate are considerably more active than the phosphate are considerably more active than one havone having the theoretical phosphorus content. ing the theoretical phosphorus content.

EXAMPLE IV EXAMPLE H Commercial ferrous phosphate was tested for A senes catalysts prepared m a dehydrogenation activity with and without added manner as m Example i P' q oxlfier phosphoric acid. The salt was obtained from Alfa lnorusually referred to as magnetic iron oxide. Th1s oxide ganics, Inc and was designated b catalog number F has the formula 3 4, and 15 generally wnsidel'ed to 164. After addition of the indicated amount of be FeO. Fe 0 Preparation details and oxidative conphosphoric acid, the catalysts were calcined 3 hours at version results are: l,000 F. The amount of 85 percent H PO added per 100 g of iron phosphate, the phosphorus content, and Time, the oxidative conversion-results are: Amount Used, pbw hours Cal- P 1 st Cat. 85% dry-cmwt% No HOHIPO g g Com, Selec CSV No. 85% H PO, Added, pbw P. wt% conv. selec CSV l3 Nonel7.3(a) Si 74 I25 6 200 l50(b80 (c) 2 -l9.6 64 86 150 I4 22.6l9.3 77 82 I59 7 30 40 54.4 18 2 21.8 s3 83 166 15 "45222.8 87 88 175 8 150 800580 (d) 3 25.2 84 85 I69 I6 90.4271 58 97 155 (a) Theoretical for Fe,(PO (a) Theoretical for A Fe,(PO 2 FePO. l9.6 weight percent. (b) Fisher magnetic iron oxide. Item 1-119. Catalog No. 64-C. This It apparent that catalysts comamfng more material was used in preparing catalysts 13-19. phosphorus than that required for the formauon of the (vlwflshedthomushlym remove p p f f ferric or ferrous phosphate are considerably more ac- (dlHea'ed abmc'hwrsmabw'zoow berm: tive than the ones having theoretical phosphorus content. It is again apparent that those catalysts containing more Th d given i E l i i that phosphorus contents greater than the stoichiometric amount required for the formation of iron phosphate can be used in the process of the invention.

EXAMPLE V Catalyst 17 was formed by first preparing a solution by dissolving 85 parts by weight of FeSO -7H O in 300 parts by weight of distilled water, and a second solution by dissolving 30 parts by weight of Na i-IP in 250 parts by weight of distilled water. The second solution was slowly added with stirring to the first solution. A precipitate formed and was aged, with stirring, in the mother liquor for 30 minutes before filtering. The filtered precipitate (ferrous phosphate) was impregnated with 9.7 parts by weight of 85 weight percent phosphoric acid and calcined at l,000 F for 4 hours. The resulting catalyst had a phosphorus content of 22.4 weight percent.

This catalyst was tested by dehydrogenating 2- methylbutene-2 to isoprene at feed, air, and steam space rates of 200, 1,000, and 4,000, respectively, a temperature of 1,000 F, and essentially atmospheric pressure. The results are shown below:

As illustrated, the data demonstrate excellent com version selectivity values for this catalyst over the 3-% hour oxidative conversion period.

EXAMPLE VI In this example, ferrous pyrophosphate (Fe P O was formed and impregnated with phosphoric acid to form other active catalysts of this invention.

A first solution was formed by dissolving 85 parts by weight of FeSO,-7H O in 300 parts by weight of distilled water, and a second solution was formed by dissolving 67 parts by weight of Na P O 'l0 H 0 in 1,000 parts by weight of distilled water. The second solution was added slowly to the first solution while stirring rapidly. A precipitate formed (ferrous pyrophosphate) and was filtered. One-third of the precipitate was washed with acetone and impregnated with 6.5 parts by weight of 85 weight percent phosphoric acid, and calcined 4 hours at 1,000 F to form catalyst 18 which contained 24.1 weight percent phosphorus. Two-thirds of the precipitate was impregnated, without washing, with l3.l parts by weight of 85 weight percent phosphoric acid and calcined at 1,000 F for 4 hours to form catalyst 19 which contained 25.3 weight percent phosphorus.

Catalystsl 8 and 19 were tested by dehydrogenating 2-methylbutene-2 to isoprene at feed, air, and steam space rates of 200, 1,000, and 4,000 respectively, a temperature of 1,000 F, and essentially atmospheric pressure. The results are shown belowi V Catalyst Time on stream, hr conversion selectivity CSV 18 V4 76 89 165 18 1 77 84 161 l9 /4 79 81 160 19 l 76 93 163 19 3 85 88 173 The data'above clearly demonstrate that catalysts l8 and 19 have an excellent conversion-selectivity value.

EXAMPLE VII Catalyst 20 was prepared by thoroughly admixing 0.2 mole of ferric chloride hexahydrate and 0.2 mole of monobasic ammonium phosphate. The resulting admixture was dried approximately l2 hours at 212 F and calcined by increasing the temperature to 1,250 F over a 4-hour period. The calcined material contained 2L6 weight percent phosphorus and was tested in the form of particles which had a size of 14-28 mesh (Tyler) by dehydrogenating 2-methylbutene-2 to isoprene at feed, air, and steam space rates of 200, 1,000, and 5,000, respectively, a temperature of 1,000 F and essentially atmospheric pressure. The results are shown below:

Time on stream, hr

Catalyst conversion selectivity CSV 20 3 V4 65 A (a) 83 86 169 (a) The catalyst was regenerated after 3 A hours on stream by simply stopping the hydrocarbon flow for 4 hours. This sample was taken V4 hour after restarting hydrocarbon flow.

The above run indicates that catalyst 20 is a highly active oxidative conversion catalyst.

EXAMPLE VIII A catalyst was prepared by calcining'a slurry of Fe,,(), and excess H PO, so that the final phosphorus content was 20.3 weight percent. The catalyst was tested for oxidative conversion of l,3-butadiene at 14.7 psia and at the indicated temperatures and gaseous hourly space rates (GHSV):

A catalyst was prepared by impregnating a precipitated ferrous phosphate with excess phosphoric acid such that the final phosphorus content was 22.4 weight percent. The catalyst was tested for oxidation conversion of 2-methylbutene-2 at 14.7 psia and at the indicated temperature and gaseous hourly space rates:

Per Pass Yield, TABLE A GHSV :nol percento I d h H 'r steam so rene x gene is Temp F films- 3 m p Pr oducts" (Catalyst A) On-stream time, I 5 hours Conversion Selectivlty i000 200 i000 4000 59 6.6

l s4 s5 40 75 78 *Furfural, acctaldchyde and acetic acid. 55 57 76 I O Regenerated by shutting oft hydrocarbon and steam flows or one hour EXAMPLE X K 58 7s Cooled catalyst to 300F and added 1 ml of 35 weight percent phosphoric acid solution. A catalyst was prepared by calcining a slurry of I5 I 89 83 Fe o. and excess phosphoric acld such that the final 2 91 33 phosphorus content was 24.0 weight percent. The $322 3% catalyst was tested for oxidative conversion of isoprene at l4.7 psia and at the indicated temperature and gaseous hourl s ace rates:

y P lt ls apparent that alr regeneratlon dld not lmprove catalyst activity, but that the addition of phosphoric acid did. GHSV Per Pass Yield, mol percent Temp F lsoprene air steam Furfural Acetic Acetal- TABLE B acid dehyde (Catalyst B) 1000 200 i000 4000 0.]! 0.03l 0.04

On-stream tlme hours Conversion Selectivity P I 17 A 77 81 EXAM LE X 64 $6 57 I 73 Regenerated by shutting off hydrocarbon flow Catalyst A 618 grams of 85 weight percent for 30 mmutes 58 7| phosphoric acid was added to a slurry of 150 grams of ml fi y divided z s l0 cooled Fe o in 800 milliliters of deionized water, the mixture 5 cm {2* 87 85 was dried for 6 hours at 200 F, calcined for 3 hours at 36 75 88 about 100 F, ground, and screened. The final 2 22 3; Phosphorus content was Weight perceflt- I Added 2 ml of finely divided no, to cooled Catalyst B 618 grams of 85 welght percent catalyzt 8 84 phosphoric acid was added to a slurry of 200 grams of 32 80 84 to Fe o, in 1500 milliliters of deionized water, and the resulting mixture was washed thoroughly to remove excess phosphoric acid. To 34 of the resulting material was added 34 grams of 85 weight percent phosphoric acid. The material was calcined for 2 hours at about l,000 F, ground, and screened. The final phosphorus content was 25.5 weight percent.

Catalyst C grams of 85 weight percent phosphoric acid was added to 100 grams of ferrous phosphate, the mixture was calcined for 3 hours at about 100 F, ground, and screened. The final phosphorus content was 22.8 weight percent.

Catalyst D sufficient 85 weight percent phosphoric acid was added to precipitated ferrous phosphate to give a final phosphorus content of 22.4 weight percent, and the mixture was calcined 3 hours at about 1,000 F, ground, and screened.

All catalysts were tested for oxidative conversion of Z-methylbutene-Z, primarily to isoprene. The respective feed, air, and steam space rates used in testing catalysts A and B were 200, L000, and about 5,000 volumes per volume of catalyst per hour. The respective feed, air, steam space rates used in testing catalysts C and D were 400, 2,000, and about 9,000 volumes per volume of catalyst per hour. The tests were made at l,O00 F and atmospheric pressure. Conversion and selectivity to isoprene are given in the following tables.

It is apparent that air/steam regeneration did not improve catalyst activity, but that addition of P 0 did.

TABLE C (Catalyst C) On-stream time.

hours Conversion Selectivity It is apparent that continuous addition of phosphoric acid can be used to maintain catalyst activity.

Catalyst D was used under a variety of conditions over a 300-hour period. Phosphoric acid was added continuously at a variety of rates during the run to maintain catalyst activity. Typical results are:

TABLE D (Catalyst D) Phosphoric Acid Orr-Stream time Addition rate hours moles per mole Conversion Selectivity of olefin feed 154(a) 342x ll) 73 94 278 l 71 X i 67 96 298 (b) l7l X ii) 86 87 (a) temperature of I025F. (h) temperature of l 100F.

lclaim:

1. An oxidative dehydrogenation conversion process comprising a. admixing at leastone dehydrogenatable organic compound with molecular oxygen or molecular oxygen-containing gas, wherein said dehydrogenatable organic compound is an alkene or alkadiene of three to carbon atoms per molecule, cycloalkene or cycloalkadiene of four to 10 carbon atoms per molecule, alkylpyridine or alkyl aromatic of one to four alkyl groups per molecule which alkyl groups contain up to six carbon atomsper group such that at least one alkyl group contains at least two carbon atoms, and

contacting said admixture from said step (a) under oxidative dehydrogenation conversion conditions with an oxidative dehydrogenation catalyst composition consisting essentially of iron-phosphorusoxygen wherein the phosphorus content thereof represents 1.01 to 5 times 4 the stoichiometric amount of said phosphorus required to react with all of said'iron in the form of phosphatmand wherein the oxygemphosphorus atomic ratio in said catalyst composition ranges from about 3:! to 3.999:l.

2. The process of claim I wherein said amount of phosphorus is from 1.0l to 2 times said stoichiometric amount.

3. The process of claim 1 wherein said iron is in the ferric form.

4. The process of claim 1 wherein said iron is in the ferrous form.

5. The process of claim 1 wherein said iron is in the ferroso-ferric form.

6. The process of claim 1 wherein said alkenes and alkadienes contain four to six carbon atoms per molecule, said cycloalkenes and cycloalkyldienes contain four to six carbon atoms per molecule, said alkylpyridines or said alkylaromatics contain one to two alkyl groups per molecule wherein said alkyl groups contain two to six carbon atoms per group.

7. The process oiclaim 1 carried out using a temperature in the range of about 700 to about l,300 F, a pressure in the range of about 0.05 to about 250 psia, an oxygen-to-gaseous organic compound feed volume ratio in the range of about 0.01/ l to about 3/1, and an organic compound feed space rate in volumes of organic compound feed vapor per volume of catalyst per hour at 32 F and 14.7 psi in the range about 50 to about 5,000.

8. The process of claim 7 further employing steam in said admixture at a steam feed volume ratio to organic feed volume in the range of about 0. ll l to about /1 9. The process of claim 8 wherein said organic compound feed comprises isopentenes.

10. The process of claim 9 wherein said organic compound feed comprises 2-methylbutene-2.

l l. The process of claim 8 wherein said organic compound ieed comprises 1,3-butadiene.

12. The process of claim 9 wherein said organic compound feed comprises isoprene.

13r The process of claim 1 wherein the activity of said catalyst is maintained by the addition of at least one phosphorus-containing compound to the reaction stream.

14. The process of claim 13 wherein said phosphorus-containing compound is phosphoric acid.

15. The process of claim 13 wherein said phosphorus-containing compound is phosphorus pentoxide.

16. The process of claim 6 wherein said dehydrogenatable organic compound is said alkylpyridines or said alkylaromatics. 

1. An oxidative dehydrogenation conversion process comprising a. admixing at least one dehydrogenatable organic compound with molecular oxygen or molecular oxygen-containing gas, wherein said dehydrogenatable organic compound is an alkene or alkadiene of three to 10 carbon atoms per molecule, cycloalkene or cycloalkadiene of four to 10 carbon atoms per molecule, alkylpyridine or alkyl aromatic of one To four alkyl groups per molecule which alkyl groups contain up to six carbon atoms per group such that at least one alkyl group contains at least two carbon atoms, and b. contacting said admixture from said step (a) under oxidative dehydrogenation conversion conditions with an oxidative dehydrogenation catalyst composition consisting essentially of iron-phosphorus-oxygen wherein the phosphorus content thereof represents 1.01 to 5 times the stoichiometric amount of said phosphorus required to react with all of said iron in the form of phosphate, and wherein the oxygen:phosphorus atomic ratio in said catalyst composition ranges from about 3:1 to 3.999:1.
 2. The process of claim 1 wherein said amount of phosphorus is from 1.01 to 2 times said stoichiometric amount.
 3. The process of claim 1 wherein said iron is in the ferric form.
 4. The process of claim 1 wherein said iron is in the ferrous form.
 5. The process of claim 1 wherein said iron is in the ferroso-ferric form.
 6. The process of claim 1 wherein said alkenes and alkadienes contain four to six carbon atoms per molecule, said cycloalkenes and cycloalkyldienes contain four to six carbon atoms per molecule, said alkylpyridines or said alkylaromatics contain one to two alkyl groups per molecule wherein said alkyl groups contain two to six carbon atoms per group.
 7. The process of claim 1 carried out using a temperature in the range of about 700* to about 1,300* F, a pressure in the range of about 0.05 to about 250 psia, an oxygen-to-gaseous organic compound feed volume ratio in the range of about 0.01/1 to about 3/1, and an organic compound feed space rate in volumes of organic compound feed vapor per volume of catalyst per hour at 32* F and 14.7 psi in the range about 50 to about 5,000.
 8. The process of claim 7 further employing steam in said admixture at a steam feed volume ratio to organic feed volume in the range of about 0.1/1 to about 100/1.
 9. The process of claim 8 wherein said organic compound feed comprises isopentenes.
 10. The process of claim 9 wherein said organic compound feed comprises 2-methylbutene-2.
 11. The process of claim 8 wherein said organic compound feed comprises 1,3-butadiene.
 12. The process of claim 9 wherein said organic compound feed comprises isoprene.
 13. The process of claim 1 wherein the activity of said catalyst is maintained by the addition of at least one phosphorus-containing compound to the reaction stream.
 14. The process of claim 13 wherein said phosphorus-containing compound is phosphoric acid.
 15. The process of claim 13 wherein said phosphorus-containing compound is phosphorus pentoxide. 